<!DOCTYPE html>
<html lang="en">
<body>
  <picture>
    <source src="snow.jpg?as=webp&width=400" type="image/webp" />
    <source src="snow.jpg?as=jpg&width=400" type="image/jpeg" />
    <img src="snow.jpg?as=jpg&width=800" alt="snow" />
  </picture>
</body>
</html>
